Influenza virus is a significant causative agent of acute lower respiratory tract infections in humans. It transmits readily, resulting in annual epidemics that can manifest in severe illness and death for high-risk populations. It is one of the RNA viruses of the family Orthomyxoviridae that affects birds and mammals, and is responsible for the illness commonly referred to as the “flu”. The most common symptoms of the flu are chills, fever, sore throat, muscle pains, severe headache, coughing, weakness/fatigue and general discomfort. Sore throat, fever and coughs are the most frequent symptoms. In more serious cases, influenza causes pneumonia, which can be fatal, particularly for the young and the elderly. Although it is often confused with other influenza-like illnesses, especially the common cold, influenza is a more severe disease than the common cold and is caused by a different type of virus. Influenza may produce nausea and vomiting, particularly in children, but these symptoms are more common in the unrelated gastroenteritis, which is sometimes called “stomach flu” or “24-hour flu”.
Typically, the influenza virus is transmitted through the air by coughs or sneezes, creating aerosols containing the virus. Influenza can also be transmitted by direct contact with bird droppings or nasal secretions, or through contact with contaminated surfaces. Airborne aerosols have been thought to cause most infections, although which means of transmission is most important is not absolutely clear.
Influenza remains a constant threat, as new variants emerge seasonally. Annual epidemics take an economic toll through lost workforce productivity, while straining health service resources. Additionally, influenza virus is responsible for major pandemics every 10-50 years. In 2009, a new H1N1 triple re-assortment of swine influenza emerged in North America and reached pandemic proportion (Zimmer and Burke, 2009). Influenza virus' ability to mutate (antigenic drift), as well as re-assort with other influenza viruses from different mammalian species (antigenic shift), are mechanisms causing seasonal epidemic variation and pandemic virus insurgence, respectively (Chen and Deng, 2009). Moreover, resistance to available anti-influenza agents is increasing. The majority of H3N2 isolates and 2009 H1N1 are resistant to the adamantane M2 ion channel inhibitors (Deyde et al, 2009). Furthermore, 2008 H1N1 has shown resistantance to the neuraminidase inhibitor Tamiflu (Oseltamivir), the standard of care (Moscona, 2009). Neither class has been shown to be effective against highly pathogenic H5N1 avian virus (Soepandi, 2010).
Multiple novel therapeutic and prophylactic agents against influenza virus are therefore currently needed in the art. Also needed are new compositions and formulations containing these agents, as well as new methods for preventing and treating influenza utilizing these agents.